Scanning neighboring base stations in wireless access system

ABSTRACT

Scanning neighboring base stations in a wireless access system is provided. In one embodiment, a method of scanning neighboring base stations for assessing channel quality includes receiving from a serving base station information associated with at least one neighboring base station, and transmitting a scanning request message from a mobile subscriber station to the serving base station, wherein the scanning request message comprises a requested scan duration and a requested scan iteration, the requested scan iteration being associated with a requested number of iterations of the scanning of the at least one neighboring base station. The method also includes receiving a scanning response message from the serving base station, wherein the scanning response message comprises an allowed scan duration and an allowed scan iteration, the allowed scan iteration being associated with an allowed number of iterations of the scanning of the at least one neighboring base station.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. § 119(a), this application claims the benefit ofearlier filing date and right of priority to Korean Application No.10-2004-0041541, filed on Jun. 7, 2004, and Korean Application No.10-2004-0046708, filed on Jun. 22, 2004, the contents of which arehereby incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to a wireless access system, andmore particularly to scanning neighboring base stations in a wirelessaccess system.

BACKGROUND OF THE INVENTION

The IEEE802.16e system is part of a global standardization for broadbandwireless access systems. IEEE802.16e does not have a hierarchicalstructure of HLR, VLR, MSC, BSC, RNC, etc. unlike second and thirdgeneration mobile communications systems, but does include a mobilesubscriber station (MSS), a base station (BS), and an authenticationservice authorization server (ASA server). A physical (PHY) layer and amedium access control (MAC) layer are defined between the BS and theMSS.

FIG. 1 is a block diagram illustrating a related art broadband wirelessaccess system in which a handover operation is performed on a dataplane. FIG. 2 is a block diagram illustrating a related art broadbandwireless access system in which a handover operation is performed on acontrol plane.

Referring to FIG. 1 and FIG. 2, a handover in a broadband wirelessaccess system is performed according to IEEE802.16e, as explained below.

1. Pre-Processing for Handover

Pre-processing for handover includes broadcasting associated informationfrom a base station to a neighboring base station to inform all mobilesubscriber stations within a respective cell of the associatedinformation (Network Topology Advertisement). The pre-processing alsoincludes measuring a channel quality of the neighboring base stationbased on the associated information (MSS Scanning of Neighboring BS).The pre-processing also includes matching parameters between the basestation and the neighboring base station, such as for example, aninitial mobile subscriber station power, a time difference forsynchronization, and other parameters (Association Procedures).

a. Network Topology Advertisement

In network topology advertisement, the base station broadcastsinformation associated with network configuration to all mobilesubscriber stations within a cell via a MOB_NBR-ADV MAC message, therebyproviding all mobile subscriber stations within the cell with theinformation pertaining to neighboring base stations.

b. MSS Scanning of Neighboring BS

In MSS scanning of neighboring BS, a mobile subscriber station (MSS)scans a neighboring base station (BS) and requests a scanning intervalfor scanning the neighboring BS from the BS via a MOB_SCN-REQ MACmessage. The BS then transmits a MOB_SCN-RSP MAC message in response tothe request to assign an interval for scanning (scanning interval) theneighboring BS. Alternatively, the BS may directly transmit theMOB_SCN_RSP MAC message without a request from the MSS (unsolicitedresponse). In the case of an unsolicited response, the scanning intervaland an offset unit for scanning start are assigned on a frame unitbasis.

c. Association Procedures

During association procedures, the MSS performs a ranging process with aBS to normally join a cell. In the ranging process, the MSS acquiresbasic information for communications from the BS. In other words, theMSS performs BS scanning to select a new BS and then performs theassociation procedures. The MSS and the BS transmit a RNG_REQ MACmessage and a RNG_RSP MAC message, respectively, to set values such asfor example, a power offset value, a timing offset value, and othervalues of the MSS to suitable values. Transmission of the RNG_REQ MACmessage is called an initial ranging operation and is a basic operationthat the MSS may perform in a network entry procedure. When a handoveris performed, a target BS accepts a new MSS and transmits itemsassociated with the respective cell of the new MSS to the former servingBS and stores information pertaining to the MSS.

2. Handover Process

In a handover (HO) process, the MSS initiates handover with theneighboring BS based on the channel quality information acquired in thehandover pre-processing.

a. Cell Selection

FIG. 3 is a diagram illustrating a related art cell selection procedurein a related art broadband wireless access system. In a cell selectionprocedure, a cell is changed to enable the MSS to make a newregistration to a BS, allowing for reception of a signal having an SINR(signal to interference noise ratio) superior to that of a signaltransmitted from the BS of the current cell, prior to a normalregistration of the MSS to a cell. In such case, since the MSS does notperform the registration procedure, the BS is unable to determine amoving situation of the MSS.

b. HO (handover) Initiation

In HO initiation, a handover may be initiated by the MSS or the BS. Whenthe BS requests (initiates) a handover, the BS transmits a MOB_BSHO-REQMAC message to the MSS. On the contrary, when the MSS requests ahandover, the MSS transmits a MOB_MSSHO-REQ MAC message to the BS.

If the MSS transmits the MOB_MSSHO-REQ MAC message, the MSSpreferentially transmits the SINR of a signal received from aneighboring BS to the BS to enable the MOB_MSSHO-REQ MAC message to betransmitted to a current serving BS. The current serving BS then selectsa candidate BS as a target BS for performing the handover. In a casewhere the BS receives the MOB_MSSHO-REQ MAC message from the MSS or in acase when the BS has not yet transmitted the MOB_BSHO-REQ MAC message tohandover the MSS, the BS may allow the handover of the MSS afterconfirmation of an acknowledgement (ACK) for handing over a specific MSSfrom the neighboring BS. After receiving the MOB_BSHO/MSSHO-REQ MACmessage, the MSS/BS transmits a MOB_MSSHO/BSHO-RSP MAC message to informthe BS/MSS of a target BS for the handover.

c. HO Cancellation

In HO cancellation, after the MSS/BS transmits the MOB_MSSHO/BSHO-REQMAC message, the MSS may cancel the handover. In canceling the HO, theMSS sets a specific field (HO_Type=01) of a MOB_HO-IND MAC message andtransmits the set field to the BS. The BS receives the message andcancels the proceeding handover.

d. Termination with the Serving BS

In termination with the serving BS, the MSS transmits the MOB_HO-IND MACmessage to inform the serving BS that the handover is normally completedand then completes the handover operation. In completing the handoveroperation, the MSS sets a specific field (HO_Type=00) of the MOB_HO-INDMAC message to transmit the information pertaining to the normalhandover termination to the serving BS. The serving BS receives theMOB_HO-IND MAC message from the MSS and terminates a MAC state machineallocated to the MSS. The serving BS also terminates an ARQ (automaticrepeat request) connection and all connections associated with datatransmission.

e. HO Rejection

In HO rejection, the MSS is capable of rejecting a handover recommendedby the BS. In rejecting a handover, the MSS sets a specific field(HO_Type=10) of the MOB_HO-IND MAC message and transmits the message tothe BS. The BS receives the rejection message from the MSS, re-seeks fora target BS and re-transmits the MOB_BSHO-RSP MAC message to the MSS.

3. Neighboring BS Scanning Procedure

FIG. 4 is a diagram illustrating a related art neighboring base stationscanning procedure. Referring to FIG. 4, a serving BS connected to anMSS broadcasts information pertaining to neighboring BSs to all MSSswithin a BS domain.

The information pertaining to the neighboring BSs is delivered via aMOB-NBR-ADV message. A configuration of the MOB-NBR-ADV message is shownin Table 1.

TABLE 1 Syntax Size Notes MOB-NBR- ADV_Message_Format( ){ ManagementMessage Type = 49 8 bits Operator ID 24 bits  Unique ID assigned to theoperator N_NEIGHBORS 8 bits For(j=0; j<N_NEIGHBORS; J++){ NeighboringBS-ID 48 bits  Physical Frequency 32 bits  Configuration Change Count 8bits Hysteresis threshold 8 bits MAHO report period 8 bits TVL EncodedNeighbor information Variable TLV specific } }

Referring to Table 1, the MOB-NBR-ADV message includes a neighboring BSnumber, a neighboring BS identifier, a neighboring BS frequency,neighboring BS channel information, and other information.

After the MSS receives the MOB-NBR-ADV message, the MSS temporarilystops receiving data transmitted from the serving BS and transmits aMOB-SCN-REQ message for acquiring a time for channel quality measurementfrom the neighboring BS to the BS. A configuration of the MOB-SCN-REQmessage is shown in Table 2.

TABLE 2 Syntax Size Notes MOB_SCN_REQ_Message_format( ){ ManagementMessage Type = 50 8 bits Scan Duration 12 bits  Units are framesReserved 4 bits }

While the MSS measures channel qualities of the neighboring BSs, theserving BS stops transmitting data to the MSS is then able to transmitdata after receiving a scanning duration request from the MSS. Theserving BS transmits a MOB-SCN-RSP message to the MSS in response to theMOB-SCN-REQ message. A configuration of the MOB-SCN-REQ message is shownin Table 3.

TABLE 3 Syntax Size Notes MOB_SCN_RSP_Message_format( ){ ManagementMessage Type = 50 8 bits Scan Duration 12 bits  Units are frames StartFrame 4 bits }

As shown in the MOB-SCN-REQ message, the BS secures the scanningduration requested by the MSS, and the MSS starts the BS scanning afterstanding by for a start frame time.

The related art neighboring BS scanning method has several problems anddisadvantages. In order to provide a seamless service from the BS, amoving MSS may request the handover. Alternatively, the BS may requestthe handover in order to balance its load. If the BS requests thehandover, the MSS performs scanning on neighboring BSs to decide whetherto perform the handover. If the handover is needed, the neighboring BSsmust be continuously scanned. However, in order to obtain channelquality information in the related art method, the MSS must transmit thescanning request message and receive the corresponding scanning responsemessage each time. Hence, the MSS continually occupies limited radioresources and unnecessarily consumes power for message transmission andreception.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to scanning neighboringbase stations in a wireless access system that substantially obviatesone or more problems of the related art.

An object of the present invention is to provide a neighboring BSscanning method in which an mobile subscriber station (MSS) efficientlymeasures a quality of a physical channel required for a handover andtransmits a corresponding result to a base station (BS).

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, inone embodiment, a method of scanning neighboring base stations forassessing channel quality in a wireless communication system includesreceiving from a serving base station information associated with atleast one neighboring base station, and transmitting a scanning requestmessage from a mobile subscriber station to the serving base station,wherein the scanning request message comprises a requested scan durationand a requested scan iteration, the requested scan iteration beingassociated with a requested number of iterations of the scanning of theat least one neighboring base station. The method also includesreceiving a scanning response message from the serving base station,wherein the scanning response message comprises an allowed scan durationand an allowed scan iteration, the allowed scan iteration beingassociated with an allowed number of iterations of the scanning of theat least one neighboring base station.

The scanning request message may preferably further comprise a requestedinterleaving interval associated with a requested time period betweeneach scan. The scanning response message may preferably further comprisean allowed interleaving interval associated with an allowed time periodbetween each scan.

During each of the allowed interleaving interval the serving basestation and the mobile subscriber station may preferably be in a normaloperation mode. If the mobile subscriber station transmits any data tothe serving base station during the allowed scan duration then thescanning of the at least one neighboring base station may preferably beterminated.

The requested scan duration may preferably be associated with arequested time period in which the mobile subscriber station initiatesand terminates the scanning of the at least one neighboring basestation. The allowed scan duration may preferably be associated with anallowed time period in which the mobile subscriber station initiates andterminates the scanning of the at least one neighboring base station.

The scanning response message from the serving base station may furthercomprise a scan report mode, wherein the scan report mode is associatedwith a reporting frequency of the mobile subscriber station to theserving base station. The scan report mode may preferably comprise atleast one of (1) no report, (2) periodic report, and (3) event triggeredreport. The mobile subscriber station may preferably transmit a scanreport to the serving base station in response to the scan report mode.

The allowed scan duration and the allowed scan iteration may preferablybe determined by the serving base station in response to the requestedscan duration and the requested scan iteration and a network load.

In another embodiment, a method of scanning neighboring base stationsfor assessing channel quality in a wireless communication system,includes receiving from a serving base station information associatedwith at least one neighboring base station, and receiving a scanningresponse message from the serving base station, wherein the scanningresponse message comprises a scan duration and a scan iteration, thescan iteration being associated with a number of iterations of thescanning of the at least one neighboring base station.

In yet another embodiment, a method of scanning neighboring basestations for assessing channel quality in a wireless communicationsystem includes transmitting to a mobile subscriber station informationassociated with at least one neighboring base station, and transmittinga scanning response message from a serving base station, wherein thescanning response message comprises an allowed scan duration and anallowed scan iteration, the allowed scan iteration being associated withan allowed number of iterations of the scanning of the at least oneneighboring base station. The method may preferably also includereceiving a scanning request message from a mobile subscriber station tothe serving base station before transmitting the scanning responsemessage, wherein the scanning request message comprises a requested scanduration and a requested scan iteration, the requested scan iterationbeing associated with a requested number of iterations of the scanningof the at least one neighboring base station.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings. It is to be understood that both the foregoinggeneral description and the following detailed description of thepresent invention are exemplary and explanatory and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a block diagram illustrating a broadband wireless accesssystem in which a handover operation is performed on a data plane.

FIG. 2 is a block diagram illustrating a broadband wireless accesssystem in which a handover operation is performed on a control plane.

FIG. 3 is a diagram illustrating a cell selection procedure in abroadband wireless access system.

FIG. 4 is a diagram illustrating a neighboring base station scanningprocedure.

FIG. 5 is a diagram illustrating a neighboring base station scanningprocedure, according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In one embodiment, a request to perform a scan for channel qualitymeasurement (scanning request message) of neighboring base stations issent to a serving base station (BS). A mobile subscriber station (MSS)transmits a cycle and an iteration count for performance of the scan(scanning) to the serving BS to enable periodic scanning. In periodicscanning of the neighboring BSs, the cycle for performing the scanningmay correspond to a time between scan execution intervals. The timebetween scan execution intervals may be, for example, a generalinterleaving interval for transmitting data between the MSS and theserving BS. The cycle for performing the scanning is called a normaloperation interval (interleaving interval). During the normal operationinterval, the MSS and the serving BS may communicate traffic data.Information pertaining to channel quality (channel quality information)measured by the MSS may include a signal to interference noise ratio(SINR) from a neighboring BS, a bit error rate, a quality of serviceidentifier, and other information.

An exemplary configuration of a scanning request message (scan requestmessage) is shown in Table 4.

TABLE 4 Syntax Size Notes MOB_SCN_REQ_Message_format( ){ ManagementMessage Type = 50 8 bits Scan Duration 12 bits  Units are framesInterleaving Interval X bits Scan Iteration Y bits }

Referring to Table 4, the MSS transmits information for periodic scanexecution to the serving BS using a scanning request message. Thescanning request message may include information pertaining to a lengthof a scanning duration (scan duration), a time to start the scanning(start frame), a count of iterated scanning (scan iteration), and ageneral function execution interval (interleaving interval). In responseto receipt of the scanning request message, the serving BS transmits ascanning response message to the MSS.

An exemplary configuration of the scanning response message is shown inTable 5.

TABLE 5 Syntax Size Notes MOB_SCN_RSP_Message_format( ){ ManagementMessage Type = 50 8 bits Scan Duration 12 bits  Units are frames StartFrame 4 bits Interleaving Interval X bits Scan Iteration Y bits }

Referring to Table 5, the serving BS transmits the scanning responsemessage to the MSS in response to receipt of the scanning requestmessage. The scanning response message may include informationpertaining to a length of a scanning duration (scan duration), a time tostart the scanning (start frame), a count of iterated scanning (scaniteration), and a general function execution interval (interleavinginterval).

The MSS periodically measures the channel quality of the neighboring BSsbased on the information included in the scanning response messagetransmitted from the serving BS. In another embodiment, the informationpertaining to the length of a scanning duration (scan duration), thetime to start the scanning (start frame), the count of iterated scanning(scan iteration), and the general function execution interval(interleaving interval) are transmitted by the BS to the MSS in responseto the request from the MSS. Alternatively, the information pertainingto the length of a scanning duration (scan duration), the time to startthe scanning (start frame), the count of iterated scanning (scaniteration), and the general function execution interval (interleavinginterval) may be transmitted by the serving BS to the MSS without arequest from the MSS (unsolicited response).

FIG. 5 is a diagram illustrating a neighboring base station scanningprocedure, according to one embodiment of the present invention.Referring to FIG. 5, in one embodiment, a 1st BS (serving BS) 520 maypreferably store the data rather than transmit the data to an MSS 510during a scanning duration (scan duration), such as the scan durationsrelated to the 1^(st), 2^(nd), and 3^(rd) iteration intervals 555, 565,and 575, respectively, in which the MSS 510 is measuring channel qualityof neighboring BSs (target BSs), i.e. the 2^(nd) BS 530 and the 3^(rd)BS 540. The serving BS 520 may then transmit the stored data during aninterval in which the MSS 510 is not scanning the neighboring BSs 530and 540, i.e., during a general function execution interval(interleaving interval).

In another embodiment, if a data transmission time is prolonged suchthat the data transmission is not completed by a new scanning start time(start frame) of the MSS 510, the serving BS 520 may ignore the scanningstart time and continue transmitting the data. Alternatively, the datatransmission may be stopped to allow for the new scanning start time. Insuch case where the data transmission is stopped, the data transmissionmay be restarted after the scanning duration of the MSS 510 ends.

In yet another embodiment, if the serving BS 520 ignores the scanningstart time of the MSS 510 and continues transmitting the data, the MSS510 may stop performing scanning in response to a determination by theMSS 510 that the scanning duration, the general function executioninterval (interleaving interval), and the scanning iteration countassigned by the serving BS 520 via the scanning response message are nolonger valid. Also, in such case where the serving BS 520 ignores thescanning start time of the MSS 510 and continues transmitting the data,data and scanning procedures received from the serving BS 520 whichrelate to an iteration count that has not been executed may then beexecuted. Alternatively, the MSS 510 may continue scanning during thedata transmission from the serving BS 520, thereby enabling the MSS 510to perform scanning during the entire scanning duration (scanduration×scan iteration) initially assigned by the serving BS 520.

In still another embodiment, the serving BS 520 may use a result ofneighboring (target) BS channel quality measurement acquired fromscanning by the MSS 510 to determine whether to command execution of thehandover to the MSS 510. In this case, the serving BS 520 may requestthe neighboring BS channel quality measurement from the MSS 510 todetermine whether it is necessary to perform the handover. The servingBS 520 may also command execution of the handover to the MSS 510 toadjust the network load of the serving BS 520.

In yet another embodiment, the channel quality measurement request fromthe serving BS 520 to the MSS 510 may be initiated based on necessity ofthe serving BS 520. In this case, the MSS 510 transmits the result ofneighboring BS channel quality measurement (channel quality measurementresult) to the requesting (serving) BS 520. For example, the MSS 510 maypreferably send parameters including requested scan iteration,interleaving interval, and scan duration to the serving base station520. The serving BS 520 may use these received parameters in combinationwith the scheduling and data buffer capabilities of the serving BS 520.Alternatively, the serving BS 520 may change the parameters. Thetransmission of the channel quality measurement result may be executedby periodically reporting the channel quality measurement resultregardless of the time point or cycle of the measurement. Alternatively,the channel quality measurement result may be reported each time the MSS510 measures the channel qualities. The measurement reporting method ofthe MSS 510 may be selected by the serving BS 520 or the MSS 510.

An exemplary configuration of a scanning response message including theinformation pertaining to the selection is shown in Table 6.

TABLE 6 Syntax Size Notes MOB-SCN- RSP_Message_Format( ){ ManagementMessage Type = 50 8 bits Scan Duration 12 bits  Units are frames StartFrame 4 bits Interleaving Interval X bits Scan Iteration Y bits ScanReport Mode 2 bits 00: no report 01: periodic report 10: event triggeredreport 11: reserved Scan Report Period Z bits Available when the valueof Scan Report is set to 01 }

The MSS may preferably report the channel quality measurement resultaccording to an identifier of the scanning response message receivedfrom the serving BS at each measurement. Alternatively, the MSS maypreferably report the channel quality measurement result according to anidentifier of the scanning response message received from the serving BSperiodically. In the case of reporting the channel quality measurementresult periodically, a separate measurement result report period may beset. Alternatively, the MSS may not report the channel qualitymeasurement result.

In one embodiment, the MSS is not required to send a confirm message inresponse to receiving the scanning response message from the serving BS.For example, if the MSS performs an action different from that commandedby the serving BS, the serving BS may determine that the scanningresponse message is incorrect and send another scanning responsemessage.

When a message requesting a new scanning and report is received from thetarget BS while the target BS is in the process of reporting a scanningresult to the serving BS, the MSS may ignore all current scanning andreport procedures and may perform a scanning and report procedureaccording to the new request message.

Periodically repeated scan duration and interleaving intervals thatenable data transmission and/or reception may be interrupted by arequest from the serving BS. When the serving BS requests such aninterruption, the serving BS may fill a specific entry (scan duration,interleaving interval, scan iteration) in the scanning response messageshown in Table 5 with a specific value, e.g., 0, for notificationpurposes. Furthermore, repeated scan duration and interleaving intervalsthat enable data transmission and/or reception may also be interruptedby a request from the MSS. When the MSS requests such an interruption,the MSS may fill a specific entry (scan duration, interleaving interval,scan iteration) in the scanning request message shown in Table 4 with aspecific value, e.g., 0, for notification purposes.

In one embodiment, a method of scanning neighboring base stations forassessing channel quality in a wireless communication system includesreceiving from a serving base station information associated with atleast one neighboring base station, and transmitting a scanning requestmessage from a mobile subscriber station to the serving base station,wherein the scanning request message comprises a requested scan durationand a requested scan iteration, the requested scan iteration beingassociated with a requested number of iterations of the scanning of theat least one neighboring base station. The method also includesreceiving a scanning response message from the serving base station,wherein the scanning response message comprises an allowed scan durationand an allowed scan iteration, the allowed scan iteration beingassociated with an allowed number of iterations of the scanning of theat least one neighboring base station.

The scanning request message may preferably further comprise a requestedinterleaving interval associated with a requested time period betweeneach scan. The scanning response message may preferably further comprisean allowed interleaving interval associated with an allowed time periodbetween each scan.

During each of the allowed interleaving interval the serving basestation and the mobile subscriber station may preferably be in a normaloperation mode. If the mobile subscriber station transmits any data tothe serving base station during the allowed scan duration then thescanning of the at least one neighboring base station may preferably beterminated.

The requested scan duration may preferably be associated with arequested time period in which the mobile subscriber station initiatesand terminates the scanning of the at least one neighboring basestation. The allowed scan duration may preferably be associated with anallowed time period in which the mobile subscriber station initiates andterminates the scanning of the at least one neighboring base station.

The scanning response message from the serving base station may furthercomprise a scan report mode, wherein the scan report mode is associatedwith a reporting frequency of the mobile subscriber station to theserving base station. The scan report mode may preferably comprise atleast one of (1) no report, (2) periodic report, and (3) event triggeredreport. The mobile subscriber station may preferably transmit a scanreport to the serving base station in response to the scan report mode.

The allowed scan duration and the allowed scan iteration may preferablybe determined by the serving base station in response to the requestedscan duration and the requested scan iteration and a network load.

In another embodiment, a method of scanning neighboring base stationsfor assessing channel quality in a wireless communication system,includes receiving from a serving base station information associatedwith at least one neighboring base station, and receiving a scanningresponse message from the serving base station, wherein the scanningresponse message comprises a scan duration and a scan iteration, thescan iteration being associated with a number of iterations of thescanning of the at least one neighboring base station.

In yet another embodiment, a method of scanning neighboring basestations for assessing channel quality in a wireless communicationsystem includes transmitting to a mobile subscriber station informationassociated with at least one neighboring base station, and transmittinga scanning response message from a serving base station, wherein thescanning response message comprises an allowed scan duration and anallowed scan iteration, the allowed scan iteration being associated withan allowed number of iterations of the scanning of the at least oneneighboring base station. The method may preferably also includereceiving a scanning request message from a mobile subscriber station tothe serving base station before transmitting the scanning responsemessage, wherein the scanning request message comprises a requested scanduration and a requested scan iteration, the requested scan iterationbeing associated with a requested number of iterations of the scanningof the at least one neighboring base station.

Accordingly, the MSS performs scanning of neighboring BSs in a wirelessaccess system without repeatedly transmitting or receiving the scanningrequest or response messages.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1-49. (canceled)
 50. A method of scanning neighboring base stations formeasuring channel quality in a wireless communication system, the methodcomprising: transmitting information associated with at least oneneighboring base station to a mobile subscriber station; andtransmitting a scanning response message to the mobile subscriberstation, the scanning response message comprising a first scan duration,a first interleaving interval and a first scan iteration, wherein thefirst scan iteration is associated with the number of iterations of thescanning of the at least one neighboring base station, and wherein thefirst interleaving interval is interleaved between scanning intervals.51. The method of claim 50, further comprising receiving a scanningrequest message from a mobile subscriber station to the serving basestation before transmitting the scanning response message, the scanningrequest message comprising a second scan duration, a second interleavinginterval and a second scan iteration, wherein the second scan iterationis associated with the number of iterations of the scanning of the atleast one neighboring base station, and wherein the second interleavinginterval is interleaved between scanning intervals.
 52. The method ofclaim 50, wherein during each of the first interleaving interval theserving base station and the mobile subscriber station are in a normaloperation mode.
 53. The method of claim 51, wherein during each of thefirst interleaving interval the serving base station and the mobilesubscriber station are in a normal operation mode.
 54. The method ofclaim 51, wherein if the mobile subscriber station transmits any data tothe serving base station during the first scan duration then thescanning of the at least one neighboring base station is terminated. 55.The method of claim 51, wherein the second scan duration is associatedwith a time period in which the mobile subscriber station initiates andterminates the scanning of the at least one neighboring base station.56. The method of claim 50, wherein the first scan duration isassociated with a time period in which the mobile subscriber stationinitiates and terminates the scanning of the at least one neighboringbase station.
 57. The method of claim 51, wherein the first scanduration is associated with a time period in which the mobile subscriberstation initiates and terminates the scanning of the at least oneneighboring base station.
 58. The method of claim 50, wherein thescanning response message further comprises a first start frame, thefirst start frame is associated with a time to start scanning.
 59. Themethod of claim 51, wherein the scanning request message furthercomprises a second start frame, the second start frame is associatedwith a time to start scanning.
 60. The method of claim 50, wherein thefirst scan duration which is set to zero indicates the scanning requestis denied.
 61. The method of claim 51, wherein the first scan durationand the first scan iteration are determined by the serving base stationbased on the second scan duration and the second scan iteration and anetwork load.
 62. A base station configured to scan neighboring basestations for measuring channel quality in a wireless communicationsystem, the base station comprising: means for transmitting informationassociated with at least one neighboring base station to a mobilesubscriber station; means for receiving a scanning request message froma mobile subscriber station to the serving base station, the scanningrequest message comprising a first scan duration, a first interleavinginterval and a first scan iteration, wherein the first scan iteration isassociated with the number of iterations of the scanning of the at leastone neighboring base station, and wherein the first interleavinginterval is interleaved between scanning intervals; and means fortransmitting a scanning response message to the mobile subscriberstation, the scanning response message comprising a second scanduration, a second interleaving interval and a second scan iteration,wherein the second scan iteration is associated with the number ofiterations of the scanning of the at least one neighboring base station,and wherein the second interleaving interval is interleaved betweenscanning intervals
 63. The base station of claim 62, wherein the firstscan duration is associated with a time period in which the mobilesubscriber station initiates and terminates the scanning of the at leastone neighboring base station.
 64. The base station of claim 62, whereinthe second scan duration is associated with a time period in which themobile subscriber station initiates and terminates the scanning of theat least one neighboring base station.
 65. The base station of claim 62,wherein during each of the second interleaving interval the serving basestation and the mobile subscriber station are in a normal operationmode.
 66. The base station of claim 62, wherein if the mobile subscriberstation transmits any data to the serving base station during the secondscan duration then the scanning of the at least one neighboring basestation is terminated.
 67. The base station of claim 62, wherein thefirst scan duration is associated with a time period in which the mobilesubscriber station initiates and terminates the scanning of the at leastone neighboring base station.
 68. The base station of claim 62, whereinthe scanning request message further comprises a first start frame, thefirst start frame is associated with a time to start scanning.
 69. Thebase station of claim 62, wherein the second scan duration which is setto zero indicates the scanning request is denied.
 70. The base stationof claim 62, wherein the second scan duration and the second scaniteration are determined by the serving base station based on the firstscan duration and the first scan iteration and a network load.